Wilson_WWSC Posted November 26, 2008 Share Posted November 26, 2008 Hi, right now I'm in the process of rollering my 240z with Rustoleum, and fixing up some other things. One thing that has been bothering me is my car's top speed. It has a 327 sbc with a TH350 trans. I took it to the track about a year and a half ago, and about two thrids down the strip, I was at 5000 rpm, going only 85 or so mph. I haven't had the time to mess with the drive train or do much research, with college and jobs and volunteering and everything. Any suggestions? Thanks. Quote Link to comment Share on other sites More sharing options...
Challenger Posted November 26, 2008 Share Posted November 26, 2008 What did it do at that speed. Did it just loose power or shut off or.... Quote Link to comment Share on other sites More sharing options...
Wilson_WWSC Posted November 26, 2008 Author Share Posted November 26, 2008 Nothing happened, I just didnt want to keep pushing the 40 year old motor past 5000 rpm. Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted November 26, 2008 Administrators Share Posted November 26, 2008 So you have the gas pedal to the FLOOR the entire trip down the strip, engine would only rev up to 5000 RPM which just so happened to be 85 MPH? No more acceleration, no more RPM... With what little specifics you provided, this is what I come up with. Sounds like 2 separate issues. 1) The trans is in 2nd gear, didn’t shift into 3rd, hence the 80-85 MPH top speed. Either the shifter is 2nd gear instead of D/3, shift linkage needs adjustment, internal trans issues not allowing 3rd gear engagement, or possibly kick down out of adjustment. 2) Your engine is struggling to run any where near as strong as it could. It should easily rev past 5000 RPM even at 85 MPH, unless your brakes are dragging, really bad! If not the brakes, then the carb is WAY out of tune or ignition timing is WAY too far advanced or WAY too far retarded, cam timing is WAY off, clogged exhaust, clogged intake, your carb isn't opening fully with the throttle fully depressed... etc etc etc... Quote Link to comment Share on other sites More sharing options...
Wilson_WWSC Posted November 26, 2008 Author Share Posted November 26, 2008 I appreciate the responses, but I don't think I'm being clear enough. It can keep acclerating past 5000, and it is in 3rd gear. Is this top speed just the limit of the 3 speed? Any cheap fixes? I've been looking for WC T-5's but most I find are Ford's, which dont work with GM. Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted November 26, 2008 Administrators Share Posted November 26, 2008 That's much better. You are sure the trans is in 3rd gear.. Hmmm... What is the diff ratio and your tire size? Is the torque converter a high stall converter? Sounds like your rear gears are too deep and/or the converter is a high stall converter. If the converter is a high stall and is matched to the engines power band, then the engine should be able to handle more RPM and you might look into taller rear gears. The T-5 would definitely solve this issue. Quote Link to comment Share on other sites More sharing options...
Administrators RTz Posted November 26, 2008 Administrators Share Posted November 26, 2008 I guess I'm the oddball... 5000rpm with a 1:1 top gear, 3.54 butts, and 24 inch tires= 101mph. Factor in 15% converter slip and you're down to 86MPH. Assumptions aside, including speedo error and tacho error, I don't find it difficult to see 'this'. Quote Link to comment Share on other sites More sharing options...
wheelman Posted November 26, 2008 Share Posted November 26, 2008 Wilson_WWSC, Seems to me you have a few choices. 1. Swap the TH350 for a 700r4 2. Search for a GM WC T-5 that'll live behind your engine 3. Get a bell housing that'll mate a Ford WC T-5 to the 327 The simplest option is replacing the TH350 with a 700r4. Other than shortening the driveshaft and possibly moving the transmission mount back it should pretty much be a bolt in. Finding a GM WC T-5 can be difficult, I searched for 3 months before finding mine on ebay, then I had to find a bellhousing, clutch fork and slave cylinder. McCloud makes a modular SFI certified bellhousing that can be used to adapt a Ford T-5 to a GM engine. The part # is 8710-13, here is a link to a page of their website that lists the various applications they support: http://www.mcleodind.com/application_guide_pgs/MODULAR_BELL_HOUSING.html Unfortunately it's a bit spendy (around $450.00-$500.00) but then you can blow up all the Ford T-5s you want. Finding the transmission is only the start though as you'll also need a pedal assembly if your car doesn't already have a clutch pedal, a master cylinder and the plumbing. Wheelman Quote Link to comment Share on other sites More sharing options...
MastersMechanic Posted November 27, 2008 Share Posted November 27, 2008 The fastest and easiest is to get on carparts.com. Order a 2004r trans mission for $300.00, with convertor and low mileage. It is a direct swap, no trans mount mods, no driveshaft mods, and you get a .62 overdrive. You will have to get a new kick down cable (I know that's not what it is called on a 2004r and a 700r4 but I can't think of what it is called right now). It comes with a lower first gear for those burn out launches. overdrives.com has the cables. Quote Link to comment Share on other sites More sharing options...
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